Pad-acid steam nylon-cotton blend with acid and vat dyes

ABSTRACT

A process for dyeing nylon/cotton textile fabrics which comprises: 1. CO-APPLYING THE VAT AND ACID DYES AT A PH of 4-8, 2. STEAMING THE FABRIC IN THE PRESENCE OF A VOLATILE ORGANIC ACID, 3. DRYING THE FABRIC, AND 4. FIXATING THE VAT DYE IN A CONVENTIONAL MANNER, HAS BEEN FOUND TO GIVE A UNION SHADE IN A CONTINUOUS MANNER WITH GOOD UTILIZATION OF THE DYE APPLIED.

[451 Apr. 4, 1972 PAD-ACID STEAM NYLON-COTTON BLEND WITH ACID AND VATDYES [72] Inventor: Ibrahim Ahmed Aboul-Saad, Wilmington,

Del.

[73] Assignee: E. l. du Pont de Nemours and Company,

Wilmington, Del.

[22] Filed: Aug. 29, 1967 [211 App]. No.: 664,028

[52] U.S. Cl. ..8/21 B, 8/34, 8/178 R [51] lnt.Cl. ..D06p 3/82 [58]Fleld of Search ..8/24, 34, 178, 21 B [56] References Cited UNITEDSTATES PATENTS 3,503,698 3/1970 Zurbuchen et al ..8/41 3,467,485 12/1969Schaeuble ..8/54 3,137,687 6/1964 Spoerri .260/160 2,447,993 8/1948Vieira ,.8/34 3,240,553 3/1966 Paul ..8/l00 OTHER PUBLICATIONS Dyeing &Finishing Dupont Nylon Bulletin N- 194, Dec. 1965 Ward ..8/24

Primary Examiner-Donald Levy Attorney-Howard P. West, Jr.

[57] ABSTRACT A process for dyeing nylon/cotton textile fabrics whichcomprises:

l. co-applying the vat and acid dyes at a pH of 4-8,

2. steaming the fabric in the presence of a volatile organic acid,

3. drying the fabric, and

8 Claims, 1 Drawing Figure DRY PAD-ACID STEAM NYLON-COTTON BLEND WITHACID AND VAT DYES FIELD OF THE INVENTION This invention relates to animproved continuous process for dyeing nylon/cotton textile fabrics withacid and vat color to a union shade by a modified pad-steam process.

STATE OF THE ART A process for applying vat dyes to textile fibers bypigment pad process wherein the goods can be continuously padded anddeveloped without extra handling and without any chance of surfaceoxidation of the color of fiber prior to complete development of color,has been described by Vieria in US. Pat. No. 2,447,993. This process isfrequently referred to as the pad-steam process, and is preferred to thepad-jig process because it limits the migration of dye from one fiber toanother. In nylon and cotton-containing fabrics having greater than 25percent by weight of the fiber as nylon, the pad-steam process does notdye the nylon and cotton fibers to the same depth of shade. Most vatdyes, under these circumstances, produce a darker shade on cotton thanon nylon. Such a shade differential produces an effect known asfrosting" when the darker dyed cotton fibers wear away leaving a higherconcentration of nylon fibers of a lighter shade on the surface of thefabric. In order to overcome such difficulties, it has been suggestedthat the additional application of acid dyes be used in order to producean acceptable uniformity of shade on both the nylon and cotton fibers.Either the application of acid dyes on a pad-steam range followed by vatdyes or the application of vat dyes followed by acid dyes have beensuggested. However, both procedures require two processing steps whichreduce the savings that can be made in processing large quantitles offabrics by continuous process. In order to retain the economy of aone-pass continuous dyeing process, a recent development reported in theMarch, 1967 Textile Industries has been suggested which incorporates theco-application vat, and acid, or neutral dyeing premetallized dyes asused in the two-stage processes in a one-pass system, whichschematically is described as pad acid plus vat dyes/infrareddry/Thermosol/pad reducing agent/steam/wash/dry. Such a process haslimited application to provide adequate coloration for fabrics which donot require a union color between the nylon and cotton fibers. It isunsatisfactory for fabrics containing more than 25 percent nylon byweight of fibers unless excessive amounts of acid dye are utilized inorder to overcome the incomplete development of the acid dye used.

OBJECT It is the object of this invention to provide a process fordyeing nylon and cotton fabrics to a union shade in a continuous mannerwith good utilization of the dye applied. It is a further object toprovide a process for dyeing piece goods in a continuous manner, whichcan be employed in applying colors in heavy shades in a singleoperation.

STATEMENT OF THE INVENTION These objects are accomplished by the presentinvention which provides an improvement in the continuous process forunion dyeing nylon/cotton fabrics which comprises the steps of:

l. co-applying the vat and acid dyes at a pH of 4-8;

2. steaming the fabric in the presence of a volatile organic acid, suchas acetic acid;

3. drying the fabric;

4. fixating the vat dye in a conventional manner.

The fixation of the vat dye is conventionally done by (1) paddingreducing agents on the dyed fabric followed by (2) steaming, (3) washingand (4) oxidizing. The fabric may then optionally be rinsed, soaped,rinsed and dried to remove any excess of the oxidizing solution orforeign matter followed by a final drying step.

DRAWING A more complete understanding of the process of this inventioncan be obtained by reference to the drawing which forms a part of thisspecification and which contains a diagrammatical representation of howthe nylon and cotton fabrics may be dyed and developed in a continuousmanner by this process.

As diagrammatically illustrated in the drawing, the cotton/nylon fabricis (l) padded with the vat and acid dyes, (2) steamedin the presence ofan organic acid, (3) dried, (4) optionally heated to a temperaturegreater than 400 l'-'., (5) padded with a reducing agent solution, (6)steamed, (7) washed and (8) dried thereby oxidizing the vat dye.

While not wishing to be held to this explanation, it is believed thatthe critical step in the continuous process of this invention is theutilization of the acid-steaming step. In this step the nylon/cottonfabric is steamed for 3060 seconds at a temperature between 230-250 F.in the presence of a volatile organic acid such as acetic acid. Thevolatile organic acid may be present from previous preparatory stepsused on the fabric or may be present as a result of the pH adjustmentmade during the application of the dyes. In some cases it may bedesirable to add or inject the volatile organic acid into the steamer.Any organic acid capable of volatilizing at the temperature encounteredin the steaming step is suitable. It is believed that the selected aciddyes transfer from the cotton to the nylon and dye the nylon at thistime. The vat pigment which is also present is partially agglomeratedwithin the fabric, thus, minimizing the tendency to migrate to thefabric surface during the subsequent drying steps and, therefore,readily available for uniformly dyeing the cotton fiber throughout thefabric thickness. After drying the steamed fabric, it may be desireableto expose the fabric to a temperature of about 400 F. (204 C.) to 430 F.(222 C.) for at least 60 seconds in order to improve the acid dyeutility.

It is also possible to reduce the degree of migration of the vat dyesduring the steaming and drying stages by the addition of salt, such assodium chloride, or the like, which tends to form weakly bondedagglomerates of vat pigments, thereby reducing migration. If desired, ahigh padding pressure may be utilized to fracture the vat dyeagglomerates to allow their penetration into the fabric.

The following examples are given to illustrate the invention. Unlessotherwise specified the parts used are by weight.

The efficiency of acid dye utility is estimated by microscopicexamination of the dyed polyamide fiber. The color change produced byabrasion of the dyed fabric is rated on a scale of l to 5 based on theGray Scale for Evaluating Change in Color described in the AATCCTechnical Manual, 1966, page B-57.

EXAMPLE I Sodium hydrocarbon sulfonate, 7.5 grams per liter of a refinedsolution of natural gums, and 1 gram per liter formic acid is padded at150 F. (65 C.) on a 35 percent polyamide and 65 percent cotton fabricwith the padder set for 50 percent moisture retention based on theweight of fabric. Without drying the padded-fabric is passed through asteaming chamber for a 60 second exposure. The fabric is immediatelypassed to a dryer operating at 300 F. (149 C.) for a 60 second exposure.The fabric is then immediately padded with a reducing agent consistingof grams per liter of caustic soda and 100 grams per liter of sodiumhydrosulfite and again steamed for 60 seconds before rinsing. Theimpregnated fabric is then oxidized in the conventional manner in a 0.25percent chromeacetic acid solution, rinsed, soaped, rinsed, and dried.The fabric is dyed a dark green shade with good penetration and fastnessto laundering and abrasion. The acid dye utility is rated as 50-80percent and the abrasion color change is rated as 4-5 on the Gray Scale.

EXAMPLE I! The fabric of Example I is padded with a dye mixturecontaining 50 grams per liter of Vat Green 3 (Color Index No. 69500),grams per liter of Vat Green 1 (Color Index No. 59825), 10 grams perliter of Anthraquinone Blue GSS (Color Index No. Acid Blue 230), 10grams per liter of Merpacyl Orange R (Color Index No. Acid Orange 128),2 grams per liter of Sodium hydrocarbon sulfonate, 7.5 grams per literof a refined solution of natural gums, and 1 gram per liter formic acid.The pad mixture is applied at 150 F. (65 C.) and the fabric immediatelysteamed at 230 F. (110 C.) for 45 seconds before drying at 250 F. (121C.) for 90 seconds before padding on the fabric a reducing agentcontaining a 90 g/l caustic soda and 90 g/l sodium hydrosulfite. Thefabric is then steamed at 230 F. (110 C.) for 45 seconds followed byrinsing, oxidizing, soaping, rinsing, and drying as in Example I. Thefabric is uniformly dyed throughout the fabric thickness to a dark greenshade with good fastness to laundering and abrasion resistance. The aciddye utility is rated as 50-80 percent and the color change is rated as4-5 on the Gray Scale.

EXAMPLE Ill The following example illustrates the best one-pathcontinuous dyeing process that can be obtained from the prior art butwithout the steaming step. The polyamide and cotton fibers are notuniformly dyed to the same even shade. A dye mixture containing 18 gramsper liter Vat Green 8 (Color Index No. 69500), 25 grams per liter VatBlack 25 (Color Index No. 69525), 3.8 grams per liter Vat Blue (ColorIndex No. 59800), 11.25 grams per liter of Acid Green (Color Index No.61570), 7.5 grams per liter of Capracyl Orange R (Color Index No. AcidOrange 60), 7.5 grams per liter of Sodium hydrocarbon sulfonate, and 15grams per liter of a refined solution of natural gums is added on thesame fabric as used in Example I at 120 F. (49 C.) and immediatelypredried over gas-fired burners and then dried on 16 heated cans. Thefabric is immediately heated at 430 F. (221 C.) for 3 minutes followedby padding of a reducing agent containing 90 g/l caustic soda and 90 g/lsodium hydrosulfite. Fabric is then steamed for 35 seconds at 225 F.(107 C.) followed by oxidizing, rinsing, soaping, rinsing, and drying asin previous example. Inspection of the fabric shows that the cottonfibers are dyed to a darker shade than the polyamide fibers and is notfast to laundering. The color change from abrasion is rated as 2-3 onthe Gray Scale and the acid dye utility is rated as 10-20 percent.

It will be understood that various changes in the invention may be madewithout departing from the spirit and scope thereof, and therefore thisinvention is not intended to be limited except as indicated in theappended claims.

What is claimed is: g

l. A process for union dyeing of nylon/cotton fabric which comprises thesuccessive steps of l. co-applying vat and acid dyes at a pH of 4 to 8,

2. steaming the said fabric in the presence of a volatile organic acid,

3. drying the said fabric, and

4. fixating the said vat dye, said fixating step comprising theconventional steps of padding reducing agents on the dyed fabricfollowed by steaming, washing and oxidizing the fabric.

2. Claim 1 wherein said organic acid is acetic acid.

3. Claim 1 wherein said organic acid is formic acid.

4. Claim 1 wherein said drying is accomplished by exposing the saidfabric to a temperature of about 400 F. to about 430 F. for at least 60seconds to improve acid dye utility.

5. Claim 1 wherein said drying is accomplished by exposing the saidfabric to a temperature of about 250 F. to about 300 F. for from about60 to about seconds.

6. Claim 5 wherein said organic acid is formic acid.

7. Claim 6 wherein said vat dye is fixated by padding the said fabricwith a reducing agent consisting of about grams per liter of causticsoda and 100 rams per-liter of sodium hydrosulfite, steaming the said faric, rinsing the said fabric and oxidizing the said vat dye.

8. Claim 7 wherein said oxidizing is accomplished by contacting the saidfabric with a 0.25 percent chrome-acetic acid solution and said fabricis subsequently rinsed, soaped, rinsed and dried.

1. CO-APPLYING THE VAT AND ACID DYES AT A PH OF 4-8,
 2. STEAMING THEFABRIC IN THE PRESENCE OF A VOLATILE ORGANIC ACID,
 2. Claim 1 whereinsaid organic acid is acetic acid.
 2. steaming the said fabric in thepresence of a volatile organic acid,
 3. drying the said fabric, and 3.Claim 1 wherein said organic acid is formic acid.
 3. DRYING THE FABRIC,AND
 4. FIXATING THE VAT DYE IN A CONVENTIONAL MANNER, HAS BEEN FOUND TOGIVE A UNION SHADE IN A CONTINOUS MANNER WITH GOOD UTILIZATION OF THEDYE APPLIED.
 4. Claim 1 wherein said drying is accomplished by exposingthe said fabric to a temperature of about 400* F. to about 430* F. forat least 60 seconds to improve acid dye utility.
 4. fixating the saidvat dye, said fixating step comprising the conventional steps of paddingreducing agents on the dyed fabric followed by steaming, washing andoxidizing the fabric.
 5. Claim 1 wherein said drying is accomplished byexposing the said fabric to a temperature of about 250* F. to about 300*F. for from about 60 to about 90 seconds.
 6. Claim 5 wherein saidorganic acid is formic acid.
 7. Claim 6 wherein said vat dye is fixatedby padding the said fabric with a reducing agent consisting of about 100grams per liter of caustic soda and 100 grams per liter of sodiumhydrosulfite, steaming the said fabric, rinsing the said fabric andoxidizing the said vat dye.
 8. Claim 7 wherein said oxidizing isaccomplished by contacting the said fabric with a 0.25 percentchrome-acetic acid solution and said fabric is subsequently rinsed,soaped, rinsed and dried.